This invention relates to a beam adjustment assembly for a cathode ray tube.
Television receivers employing an in-line color television picture tube without internal pole pieces utilize a plurality of pairs of multi-pole magnetic rings mounted concentric with the neck of the picture tube in proximity with the electron gun to provide for an adjustment of the relative beam landings of the three electron beam produced by the electron gun to effect static convergence of the beams at the central portion of the picture viewing screen. These pairs of rings are generally mounted on a cylindrical nonmagnetic sleeve clamped to the neck of the picture tube thereby providing for axial rotation of the rings with respect to the neck of the picture tube. Upon having achieved a proper adjustment of the rings with respect to the neck of the picture tube, various techniques have been employed to provide for locking of these rings in their optimum location. One technique employed utilizes an adhesive which bonds the various rings, one to the other, and to the cylindrical sleeve clamped to the neck of the picture tube. Another technique employs a threaded collar which is screwed onto the cylindrical sleeve and provides for the application of sufficient pressure between the various rings and against a collar which is part of the sleeve clamped to the neck of the picture tube. Still another technique utilizes a second collar which snaps onto the cylindrical tube, and a third collar which is rotatably mounted with respect to the first collar in a manner which will provide for clamping of the rings with respect to the cylindrical sleeve when the third collar is rotated to a predetermined position relative to the first collar. Each of these techniques require the application of a rotational force applied to the magnet assembly and relative to the neck of the picture tube, which force may cause the magnets to be undesirably moved with respect to the neck of the picture tube during the locking procedure.